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This feature Tech-Tip will cover the usage of additional (AUX) power on the ProcessPro® Transmitters. There are
basic power requirements that are necessary to operate the transmitters and depending on what sensors and how
many sensors are connected, the power requirements can vary. If multiple sensors, relays, or high current
consuming sensors are used, then the use of AUX power must be used. See the recommendations/requirements
below.

Basic Power Requirements:

24 VDC, with current consumption ranging from 22 mA to 250 mA, depending on the measurement parameter
and the application.

Additional (AUX) Power Requirements:

      Auxiliary power is a second set of terminals that deliver power to features that cannot be powered from the
      basic loop. These features include multiple sensors for the -3 models, relay operation for -2 models, particular
      sensors with greater than 1.5mA current consumption for -1 or -3 versions, and for all conductivity (8850)
      systems.

HINT: the smallest power supply in the Signet catalog is the 7400-7524, capable of delivering up to 300 mA. This power supply is suitable for any ProcessPro® system, regardless of the circumstances and application.

RECOMMENDATION: Standardize on the 7400-7524 power supply for all ProcessPro® systems. If AUX terminals are provided, simply elect to always connect them. Even if AUX power is not necessary, connecting it will not affect the circuitry.

ProcessPro® Transmitters	Purpose
3-8250-2	AUX power required for relay use.
3-8250-3	AUX power required for dual sensor inputs.
3-8350-1	No AUX required.
3-8350-2	AUX power required for relay use.
3-8350-3	AUX power required for dual sensor inputs.
3-8450-1	No AUX required.
3-8450-2	AUX power required for relay use.
3-8450-3	AUX power required for dual sensor inputs.
3-8550-1	AUX power required for the Signet 2000, the Signet 2507 and the Signet 2551. Also required if the sensor input pulls more than 1.5 mA.
3-8550-2	AUX power required for relay operation and if sensor pulls more than 1.5 mA.
3-8550-3	AUX power required for the Signet 2000, the Signet 2507 and the Signet 2551. Also required if dual sensors are used or the sensors pull more than 1.5 mA.
3-8750-1	No AUX required.
3-8750-2	AUX power required for relay use.
3-8750-3	No AUX required.
3-8850-1	AUX power always required.
3-8850-2
3-8850-3

NOTE: The above table refers to current products as of 12/11/2006.